Under the new AIA patent law there is a window of time that starts after an application is published (has already occurred or you would not have been able to see it) and ends either 6 months later or when the first rejection has been issued by the patent office, whichever happens layer. The window would also end in the unlikely case that there was a notice of allowance issued before either of those triggers. There is info on how to do it on this site's faqs and here at the USPTO site. Up to three previously published documents can be submitted and there is a limit to any accompanying text on why the documents are relevant. More published documents can be submitted for a small fee but evidence of demonstration or use in public, itself, can not be submitted. The document submission can be done anonymously if you have it done via a USPTO registered practitioner.
To see if a rejection has been issued in the case you can look the application up in the USPTO's Public PAIR. It has an unforgiving user interface that requires you to set a radio button selecting the kind of number you are giving it. If the number looks like it starts with a year, it is a publication number. Just use the number, no "US" in front of it and no "/" between the year and the rest of the number.
If you are past the window you might consider posting all the information at Ask Patents. If the owner of any granted patent goes after someone for infringement a reasonable search might turn up the tagged info you posted here and help someone defend themselves.
You might also get users commenting on how relevant the documents might actually be.